Biomedical subjects

P M Richards

Publications and source records attributed to P M Richards.

15 recordsLinked to original sources

PubMed1998

Ontogeny of two-point discrimination for fingers and toes in children (ages 7 through 15 years).

Accuracies of two-point discrimination (successive 2-min increments between 0 and 10 mm) for the middle fingers and the middle toes for 87 children from ages 7 through 15 years were measured to obtain normative data. The finer discriminative capacity for the fingers rather than the toes was evident. Whereas discriminative accuracy approached the asymptote with distances equal to or greater than 4 mm for the fingers, distances equal to or greater than 8 mm were required for the toes. For this ontogenetic range, the effects for toes vs fingers was much greater than the effect size for age.

Adolescent↗

PubMed1998

Numbers of details in the reconstruction of an emotional narrative decrease linearly as a function of time.

33 university students listened to a 5-min. ambiguous narrative about a young boy (The Billy Story) while another 33 students did not. At the end of the final examination for the course the students were promised a 2% bonus mark if they could reconstruct the details of the story. Whereas only one student who heard the story could not recall any details, 30% of the students (n = 9) who never heard the story generated a false one. The numbers of accurate details recalled by those who heard the story decreased linearly with the time (5 through 30 days). Five times the numbers of the women than men who heard the story attributed the young boy's anomalous experience to sexual abuse.

Adult↗

PubMed1997

Differential entrainment of electroencephalographic activity by weak complex electromagnetic fields.

The hypothesis was tested that compensatory susceptibility to electroencephalographic driving and entrainment by weak (1 microT) time-varying, externally applied complex magnetic fields would occur in normal subjects following successive stimulation by different patterns. 43% of the volunteers showed evidence of driving during the application of the complex magnetic fields and indications of resonance (entrainment) during the first 10 sec. following the cessation of the fields. The volunteers who exhibited driving and entrainment could be discriminated from those who did not by their more frequent reported experiences of fear and odd tastes during the stimulation. They were also more likely to have a preexposure history of a sense of presence and to experience intense meaningfulness when reading or writing prose or poetry.

Adult↗

PubMed1995

Vestibular experiences of humans during brief periods of partial sensory deprivation are enhanced when daily geomagnetic activity exceeds 15-20 nT.

The intensity of reported vestibular experiences by normal volunteers (n = 127, over a 4-year period) increased significantly in a step-like manner during partial sensory deprivation when the daily geomagnetic activity exceeded about 15 nT; the effect size was equivalent to a correlation of about 0.33. Post hoc analyses indicated that the geomagnetic activity during the 3-h period at the beginning of the previous sleep cycle was the single greatest contributor. The enhanced occurrences of experiences that are similar to those associated with complex partial epileptic seizures suggests that specific stimuli associated with geomagnetic activity above about 15 nT affects specific regions of the human brain; the vulnerability occurs during the subsequent 24 h. However, in non-epileptic individuals these experiences must be amplified neurocognitively by removing input from auditory and visual modalities.

Adolescent↗

PubMed1995

Women reconstruct more details than men for a complex five-minute narrative: implications for right-hemispheric factors in the serial memory effect.

A total of 20 men and 20 women listened to a 5-min. ambiguous narrative (the "Billy" story). When the subjects were asked (unexpectedly) to reconstruct the details of the story as a written narrative 30 min. later, women employed about 50% more words and comparably more accurate detail than the men. Covariance for pre-experimental experiences suggested that the women's proficiency could be related to the greater representation of linguistic processes within the right (non-dominant) hemisphere. The hypothesis that the classic deficit of reconstructional accuracy for events during the middle of a story is related to right-hemispheric inhibition was also supported. Subjects who recalled the fewest details reported more vivid dreaming during the subsequent two days.

Adult↗

PubMed1995

Foot agility and toe gnosis/graphaesthesia as potential indicators of integrity of the medial cerebral surface: normative data and comparison with clinical populations.

A protocol was designed to identify quantitative indicators of the function of the medial surfaces of the cerebral hemispheres. Normative data were collected from 40 volunteers for foot agility, toe gnosis, and toe graphaesthesia. A total of 100 patients (most of whom had been referred for possible closed-head injuries) completed thorough neuropsychological and cognitive assessments. Deficits for toe graphaesthesia were most consistently correlated with general brain impairment and with scores for tasks whose normal performance requires the integrity of structures within the dorsal half of the medial cerebral hemispheres.

Adolescent↗

PubMed1994

The sensed presence as right hemispheric intrusions into the left hemispheric awareness of self: an illustrative case study.

The hypothesis of vectorial hemisphericity predicts that left hemispheric intrusions of the right hemispheric equivalent of the sense of self should be associated with the experience of a "presence" of someone else. The neurophenomenological profile of a woman whose medical history satisfied these theoretical criteria (verified electrical anomalies that could encourage phasic discharges within the right temporal lobe and atrophy within the left temporoparietal region) is presented. In addition to interactions between electrical seizures and thinking, she reported a long history of sensed presences, ego-alien intrusions, and "sudden knowing of the subsequent sequences of seizures" before they occurred clinically. The existence of these neurocognitive processes demands a reevaluation of the psychiatric default explanations of "hysteria" and questions the belief that "awareness during seizures" or "premonition of subsequent somatosensory experience" contraindicates an epileptic process.

Adult↗

PubMed1994

Alterations in pleasantness but not activation when long-term memories are reconstructed during contextual versus noncontextual settings.

Because the dorsomedial thalamus is a major input to the prefrontal cortices, the reconstruction of experience (episodic memory) that is maximally dependent upon this subcortical structure should be influenced by one of its major correlates, hedonistic tone. University men and women (ns = 20) were shown two brief video-tapes of muricide and copulation among male rats during a lecture concerning instinctual behaviors. Two weeks later the subjects were asked to recall (written narratives) all of the details of the videotapes when they were in either the same or a different context. Although both groups generated similar numbers of words and employed words with comparable activation scores, the group who reconstructed the experiences outside of the context used words with significantly lower (eta = 0.59) pleasantness scores relative to the group who remembered the videotapes within the same setting.

Adult↗

PubMed1994

Quantitative electroencephalographic validation of left and right temporal lobe signs and indicators in normal people.

During a single 20-min. exposure to partial sensory deprivation, the average duration of alpha rhythms over the left temporal lobe (T3) increased significantly compared to that for the right homologous region (T4). The percentage changes (increase) over time in the duration of alpha rhythms over the left temporal lobe but not the right temporal lobe were significantly correlated (.64) with histories of automatic behaviors (cessation of awareness) while only the relative increases over time in the durations of alpha rhythms over the right temporal lobe were correlated with histories of vestibular-auditory experiences (.42). The results suggest construct validity for differential hemispheric sources of some specific clusters of complex partial epileptic-like experiences that have been inferred to reflect the continuum of temporal lobe lability.

Adult↗

PubMed1994

Differential ratings of pleasantness following right and left hemispheric application of low energy magnetic fields that stimulate long-term potentiation.

A total of 40 normal men and women were exposed under double blind conditions for 20 min to either sham-conditions or to 1 microT (10 mG) electromagnetic fields (known to produce long-term potentiation within hippocampal slices) that were applied primarily over the right temporal lobe, over the left temporal lobe or over both temporal lobes homogeneously. The men and women who received the stimulation over the right hemisphere rated their experiences as significantly more pleasant than those who received the same stimulation over the left hemisphere [eta = 0.51]. Covariance for the variation in ambient geomagnetic activity, which was negatively correlated with pleasantness, increased the significance of the experimental treatment. The potential clinical utility of applying computer-generated local and penetrative but weak intensity complex magnetic fields over portions of the human brain is discussed.

Adult↗

PubMed1992

Severity of experimental allergic encephalomyelitis in rats depends upon the temporal contiguity between limbic seizures and inoculation.

Limbic seizures (forepaw clonus) were induced in Lewis rats by subcutaneous injections of lithium (3 mEq/kg) followed 24 h later by a muscarinic agent. Either 7 days before, 7 days after, or on the day of seizures, rats were inoculated with a spinal cord preparation. Other groups received these preparations but served as treatment (no seizure) controls. In three separate experiments, rats in which seizures had been induced at the time of inoculation displayed significant increases in the severity of clinical symptoms 14-20 days later relative to controls while rats in which seizures had been induced 7 days after inoculation displayed less severe symptoms; the latter effect was partially simulated by multiple injections of 1 mg/kg dexamethasone. The immunofacilitation effect was much stronger than the immunosuppression and explained 25-30% of the variance in the clinical severity scores.

Animals↗

PubMed1992

Experimental stimulation by burst-firing weak magnetic fields over the right temporal lobe may facilitate apprehension in women.

Intermittent bursts of weak magnetic fields whose patterns simulate normal amygdaloidal-hippocampal activity were generated by computer over the right or left temporal regions of men and women during partial sensory deprivation. As predicted, women but not men reported greater apprehension during right-hemispheric but not left-hemispheric stimulation. Intrusions of right-hemispheric processes have been hypothesized to affect self-esteem adversely. These results also support the role of the right parahippocampal region in the production of panic attacks.

Adult↗

PubMed1989

Motivational effects on neuropsychological functioning: comparison of depressed versus nondepressed individuals.

The neuropsychology of depression was examined in terms of organic and motivational hypotheses. Thirty medication-free depressed outpatients (selected according to Diagnostic and Statistical Manual of Mental Disorders [American Psychiatric Association, 1980] criteria for major depression) and 30 nondepressed normal controls were evaluated with a variety of neuropsychology measures. Prior to testing, subjects were assigned randomly to either a motivated or nonmotivated condition. A task measuring level of motivation demonstrated efficacy of the two motivation conditions. A 2 x 2 (Diagnosis x Motivational Level) multivariate analysis of variance of all the dependent measures revealed a significant main effect for depression, but no effect for motivation and no interaction. Univariate analyses demonstrated that the depressed group was impaired on visuospatial short-term memory and learning and on verbal learning. The finding of neuropsychological deficit in depressed subjects was not attributable to motivational factors. The problems with conceptualizing depression as a right-hemisphere dysfunction are discussed.

Depressive Disorder↗

PubMedDate not supplied

Seizure onset times for rats receiving systemic lithium and pilocarpine: sources of variability.

Injection of 30 mg/kg of pilocarpine 24 h after systemic injection of lithium (3 mEq/kg) results in overt limbic motor seizures within about 30 min. Results of several experiments indicated that whereas food deprivation or repeated nociceptive stimulation during the previous 24 h decreased seizure onset times (SOTs) by about 11 to 12 min, food restriction, continuous lighting, or, handling during the previous 7 to 14 days increased SOTs by comparable durations. Early handling before weaning but not injections of clomimpramine also decreased SOTs. A difference of 18 min in the means of SOTs was produced by injecting either 1.0 (increased SOT) or 1.5 mg/kg (decreased SOT) of dexamethasome during the previous 24 h. A strong (multiple r=.87) association between SOTs and the amount of damage within five specific thalamic-limbic nuclei was observed. These results, in conjunction with blood corticosterone levels taken before and after induction of the seizures, suggest the neurochemical mechanisms affecting the range in SOTs could involve the adrenocorticotropic hormone (ACTH)-corticosterone system and influence the amount of post-seizure-induced damage.

Animals↗

PubMedDate not supplied

Modification of activation and evaluation properties of narratives by weak complex magnetic field patterns that simulate limbic burst firing.

In two separate experiments a total of 71 volunteers were asked to generate spontaneous narratives that were scored automatically by the Whissell Dictionary of Affect. During the narratives, weak (1 microT; 10 mG) magnetic fields were applied briefly through the temporal planes. In Experiment I, subjects who were exposed to simple sine wave or pulsed fields generated more scorable words that indicated lower activation and evaluation than sham-field conditions. In Experiment II subjects exposed to a computer-generated wave form, designed to simulate neuronal burst firing, generated narratives dominated by more pleasantness and less activation than a reference group. The possibility that this approach could be utilized to study the affective dimension of language selection was indicated.

Adult↗